Isosorbide dinitrate is nitrate compound widely used as medicine for the treatment of ischemic heart disease, especially as an antianginal drug. It is also used as raw materials for explosive. The pharmaceutical formulations of isosorbide dinitrate such as sublingual tablet for the internal use, injection or spray formulation have been proposed, and furthermore, various kinds of tapes such as sustained releasing transdermal formulation are also proposed.
Isosorbide dinitrate is the substance which melts at 77.degree. C., and for the safety transportation, it is sold in 40% admixture powdery form with lactose. Therefore, to produce adhesive tapes containing isosorbite dinitrate, it has to be extracted from lactose admixture powdery form using organic solvent such as ethyl acetate, and the resulting organic solvent of isosorbite dinitrate is combined into the adhesive base materials. For the adhesive base material to be used for the tapes, solvent type of acrylic acid adhesive can be used. The solvent used for the acrylic acid adhesive may be the same one used for the extraction of isosorbide dinitrate, such as ethyl acetate.
However, there found to be problems such as crystallization of isosorbide dinitrate in the adhesive layer and the decreasing of adhesion when the ratio of isosorbide dinitrate of the base material is increased to achieve its high pharmaceutically effects. As a result, enough adhesion of the tapes to the skin and stable releasing of the active ingredient from the adhesive layer is not obtained.
Isosorbide dinitrate is a substance with sublimation and hygroscopic properties, and therefore, the conventional backings used for the transdermal formulation such as polyvinyl chloride film, polyester film or polypropylene film can not be used. The laminated backing composed of polyester film and another film were used for the transdermal preparation of isosorbide dinitrate; however, it was difficult to apply to the skin due to the thinness of the laminated backing.